The present invention relates, in general, to the field of integrated circuit (xe2x80x9cICxe2x80x9d) device structure and processing. More particularly, the present invention relates to a borderless transistor gate and source/drain region contact structure and processing technique of especial utility in providing an on-chip area efficient connection between the device gate layer and an associated source/drain region that can also overlap adjoining isolation structures. In a representative embodiment disclosed herein, such may be effectuated through the overlapping of one portion of the contact region over the edge of the gate polysilicon layer and another part of the contact over the source/drain diffusion.
A number of processing techniques have been described for the formation of contacts between the polysilicon interconnect layer of metal oxide semiconductor (xe2x80x9cMOSxe2x80x9d) transistor gates and an associated source/drain diffusion. Representative of these are U.S. Pat. No. 4,966,870 to Barber et al. for xe2x80x9cMethod for Making Borderless Contactsxe2x80x9d; U.S. Pat. No. 5,043,790 to Butler for xe2x80x9cSealed Self Aligned Contacts Using Two Nitrides Processxe2x80x9d; U.S. Pat. No. 5,104,822 to Butler for xe2x80x9cMethod for Creating Self-Aligned, Non-Patterned Contact Areas and Stacked Capacitors Using the Methodxe2x80x9d; U.S. Pat. No. 5,216,281 to Butler for xe2x80x9cSelf Sealed Aligned Contact Incorporating a Dopant Sourcexe2x80x9d; U.S. Pat. No. 5,385,634 to Butler et al. for xe2x80x9cSealed Self Aligned Contact Processxe2x80x9d; U.S. Pat. No. 5,652,176 to Maniar et al. for xe2x80x9cMethod for Providing Trench Isolation and Borderless Contactxe2x80x9d; U.S. Pat. No. 5,674,781 to Huang et al. for xe2x80x9cLanding Pad Technology Doubled Up as a Local Interconnect and Borderless Contact for Deep Sub-Half Micrometer IC Applicationxe2x80x9d; and U.S. Pat. No. 5,928,967 to Radens et al. for xe2x80x9cSelective Oxide-to-Nitride Etch Process Using C4F8/CO/ARxe2x80x9d. None of the techniques described in the aforementioned patents allow for the formation of a dual contact from a gate polysilicon layer to an associated diffusion that could also overlap adjoining isolation structures.
Disclosed herein is a borderless transistor gate and source/drain region contact structure and processing technique which provides an on-chip area efficient layout and connection between the device gate layer and an associated source/drain region that can also overlap adjoining isolation structures. In a representative embodiment disclosed herein, this is effectuated through the overlapping of one portion of the contact region over the edge of the gate polysilicon layer and another part of the contact over the source/drain diffusion.
Advantageously, the structure and process of the present invention provides a desirable size reduction in the contact for a given design rule dimension. The contact provided hereby is inherently xe2x80x9cself-alignedxe2x80x9d to both the gate polysilicon layer and the isolation region in that the contact has no need for an interstitial space between it and the gate polysilicon or isolation regions to prevent unintended electrical connections thereto. In the latter instance, the unwanted connection would be to the semiconductor bulk, or substrate.
Particularly disclosed herein is a method for forming an electrical contact to at least one switching device forming a portion of an integrated circuit device wherein the switching device comprises a pair of substantially coplanar, spaced apart source and drain regions formed in a substrate having a gate terminal insulatedly disposed between the source and drain regions overlying the substrate. The method comprises the steps of: forming an insulating layer overlying the gate terminal proximate to the source and drain regions; forming an antireflective layer overlying the insulating layer and the source and drain regions, with the antireflective layer having a first thickness overlying the insulating layer and a second greater thickness overlying the source, drain and isolation regions. The antireflective layer overlying the insulating layer which overlies the gate terminal is removed to a first thickness thereof and at least a portion of said second thickness of the antireflective layer overlying one of the source or drain regions is also removed by an amount substantially equivalent to the first thickness to provide a remaining third intermediate thickness thereof. The insulating layer overlying the gate terminal is selectively removed to expose an upper surface thereof without substantially removing the third intermediate thickness of the antireflective coating. The process further includes the steps of: removing the third thickness of the antireflective coating layer to expose an upper surface of one of the source or drain regions; forming at least one additional layer at least overlying remaining portions of the insulating layer overlying the gate terminal, the upper surface of the gate layer and the upper surface of one of the source or drain regions; removing a portion of the additional layer to provide an aperture formed therein at least overlying the upper surfaces of the gate terminal and one of the source or drain regions and forming the electrical contact to the gate terminal and the source of drain region within the aperture.
Also disclosed herein is a method for forming an electrical contact to at least one switching device forming a portion of an integrated circuit device wherein the switching device includes a pair of substantially coplanar spaced apart source and drain regions formed in a substrate has a gate terminal insulatedly disposed between the source and drain regions overlying the substrate. The gate terminal and an adjacent conductive region disposed laterally of one of the source and drain regions are covered by respective first and second isolation structures. The method includes the steps of: forming a photoresist layer overlying an upper surface of the integrated circuit device; forming an opening in the photoresist layer overlying at least a portion of the gate terminal and one of the source and drain regions; removing a portion of the first isolation structure overlying at least a portion of an upper surface of the gate terminal within the opening and exposing an upper surface of one of the source and drain regions; removing the photoresist layer; forming at least one additional layer overlying the upper surface of the integrated circuit device including the portion of the upper surface of the gate terminal and the upper surface of one of the source and drain regions; forming an aperture in the additional layer to expose at least the portion of the upper surface of the gate terminal, the upper surface of one of the source and drain regions and at least a portion of an upper surface of the second isolation structure; and forming the electrical contact to the gate terminal and one of the source and drain regions within the aperture.